Fig. 2

A A 54-year-old man underwent L3–L5 fusion with instrumentation and cages, and the initial postoperative X-ray showed good screw and cage positions. B One month later, the patient developed severe back pain, leukocytosis, and elevated CRP level. An X-ray revealed end plate destruction at L4–L5, posterior migration of the L4–L5 cage, and L5 screw loosening. C A posterior approach was chosen, and an intraoperative X-ray showed that the cage was pushed to the anterior region during the process of entrance enlargement with the TLIF shaver. D With an endoscopy-assisted technique, the cage was identified clearly. E A disk clamp was used to adjust the axis of the cage. F The axis of the cage was adjusted to let the connector hole for the threaded cage holder be directed along with the trajectory of the tract. F, H Thread tightening could be performed under a clear visual filed, and then the cage was retrieved